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Characterizing the high-velocity stars of RAVE: the discovery of a metal-rich halo star born in the Galactic disc

Hawkins, K.; Kordopatis, G.; Gilmore, G.; Masseron, T.; Wyse, R. F. G.; Ruchti, Gregory LU ; Bienayme, O.; Bland-Hawthorn, J.; Boeche, C. and Freeman, K., et al. (2015) In Monthly Notices of the Royal Astronomical Society 447(2). p.2046-2058
Abstract
We aim to characterize high-velocity (HiVel) stars in the solar vicinity both chemically and kinematically using the fourth data release of the RAdial Velocity Experiment (RAVE). We used a sample of 57 HiVel stars with Galactic rest-frame velocities larger than 275 km s(-1). With 6D position and velocity information, we integrated the orbits of the HiVel stars and found that, on average, they reach out to 13 kpc from the Galactic plane and have relatively eccentric orbits consistent with the Galactic halo. Using the stellar parameters and [alpha/Fe] estimates from RAVE, we found the metallicity distribution of the HiVel stars peak at [M/H] = -1.2 dex and is chemically consistent with the inner halo. There are a few notable exceptions that... (More)
We aim to characterize high-velocity (HiVel) stars in the solar vicinity both chemically and kinematically using the fourth data release of the RAdial Velocity Experiment (RAVE). We used a sample of 57 HiVel stars with Galactic rest-frame velocities larger than 275 km s(-1). With 6D position and velocity information, we integrated the orbits of the HiVel stars and found that, on average, they reach out to 13 kpc from the Galactic plane and have relatively eccentric orbits consistent with the Galactic halo. Using the stellar parameters and [alpha/Fe] estimates from RAVE, we found the metallicity distribution of the HiVel stars peak at [M/H] = -1.2 dex and is chemically consistent with the inner halo. There are a few notable exceptions that include a hypervelocity star candidate, an extremely HiVel bound halo star, and one star that is kinematically consistent with the halo but chemically consistent with the disc. High-resolution spectra were obtained for the metal-rich HiVel star candidate and the second highest velocity star in the sample. Using these high-resolution data, we report the discovery of a metal-rich halo star that has likely been dynamically ejected into the halo from the Galactic thick disc. This discovery could aid in explaining the assembly of the most metal-rich component of the Galactic halo. (Less)
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publication status
published
subject
keywords
Galaxy: abundances, Galaxy: halo, Galaxy: kinematics and dynamics
in
Monthly Notices of the Royal Astronomical Society
volume
447
issue
2
pages
2046 - 2058
publisher
Wiley-Blackwell
external identifiers
  • wos:000350272900084
  • scopus:84922496648
ISSN
1365-2966
DOI
10.1093/mnras/stu2574
language
English
LU publication?
yes
id
575cb932-963b-40e4-a0cf-562c0102900e (old id 5297236)
date added to LUP
2015-04-27 09:05:36
date last changed
2016-04-15 14:29:27
@article{575cb932-963b-40e4-a0cf-562c0102900e,
  abstract     = {We aim to characterize high-velocity (HiVel) stars in the solar vicinity both chemically and kinematically using the fourth data release of the RAdial Velocity Experiment (RAVE). We used a sample of 57 HiVel stars with Galactic rest-frame velocities larger than 275 km s(-1). With 6D position and velocity information, we integrated the orbits of the HiVel stars and found that, on average, they reach out to 13 kpc from the Galactic plane and have relatively eccentric orbits consistent with the Galactic halo. Using the stellar parameters and [alpha/Fe] estimates from RAVE, we found the metallicity distribution of the HiVel stars peak at [M/H] = -1.2 dex and is chemically consistent with the inner halo. There are a few notable exceptions that include a hypervelocity star candidate, an extremely HiVel bound halo star, and one star that is kinematically consistent with the halo but chemically consistent with the disc. High-resolution spectra were obtained for the metal-rich HiVel star candidate and the second highest velocity star in the sample. Using these high-resolution data, we report the discovery of a metal-rich halo star that has likely been dynamically ejected into the halo from the Galactic thick disc. This discovery could aid in explaining the assembly of the most metal-rich component of the Galactic halo.},
  author       = {Hawkins, K. and Kordopatis, G. and Gilmore, G. and Masseron, T. and Wyse, R. F. G. and Ruchti, Gregory and Bienayme, O. and Bland-Hawthorn, J. and Boeche, C. and Freeman, K. and Gibson, B. K. and Grebel, E. K. and Helmi, A. and Kunder, A. and Munari, U. and Navarro, J. F. and Parker, Q. A. and Reid, W. A. and Scholz, R. D. and Seabroke, G. and Siebert, A. and Steinmetz, M. and Watson, F. and Zwitter, T.},
  issn         = {1365-2966},
  keyword      = {Galaxy: abundances,Galaxy: halo,Galaxy: kinematics and dynamics},
  language     = {eng},
  number       = {2},
  pages        = {2046--2058},
  publisher    = {Wiley-Blackwell},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Characterizing the high-velocity stars of RAVE: the discovery of a metal-rich halo star born in the Galactic disc},
  url          = {http://dx.doi.org/10.1093/mnras/stu2574},
  volume       = {447},
  year         = {2015},
}